1. Field of the Invention
The invention generally relates to phased array antenna systems and, more particularly, the invention relates to an ultra-wideband, multi-beam phased array antenna.
2. Description of the Related Art
Phased array antennas exhibit desirable properties for communications and radar systems, the salient of which is the lack of any requirement for mechanically steering the transmission beam. This feature allows for very rapid beam scanning and the ability to direct high power to a target from a transmitter, or receive from a target with a receiver, while minimizing typical microwave power losses. The basis for directivity control in a phased array antenna system is wave interference. By providing a large number of sources of radiation, such as a large number of equally spaced antenna elements fed from a combination of in-phase currents, high directivity can be achieved. With multiple antenna elements configured as an array, it is therefore possible, with a fixed amount of power, to greatly reinforce radiation in a desired direction.
A significant feature of present adaptive phased array antenna systems is that they are typically narrowband. New applications for phased array antenna systems constantly push the design envelope for increasingly higher transmission frequencies and wider bandwidths. Increasing the transmission frequency, however, requires that radiating elements be placed in increasingly closer and closer proximity to one another. At the same time, the antenna element size is dictated by the lowest frequency of operation. It is found that as both the frequency of transmission and bandwidth increase, the use of multi-beam arrayed configurations of antenna system elements becomes limited by the physical space required to incorporate the system elements.
Therefore, there exists a need in the art for an ultra-wideband antenna aperture for phased array systems.
The disadvantages associated with the prior art are overcome by an ultra-wideband, adaptive antenna having a first sub-array of antenna elements disposed so as to receive RF signals located in a first sub-band of a desired frequency band, and one or more additional sub-arrays of antenna elements interspersed within the first sub-array so as to receive RF signals located in a respective one or more sub-bands of the desired frequency band. In one embodiment, the desired frequency band is divided into three sub-bands and the antenna comprises a low-, a mid-, and a high-frequency sub-array for receiving RF signals in each sub-band. The interspersed structure of the present invention allows for a signal antenna aperture for ultra-wideband phased array antenna systems.